1. Field of the Invention
The present invention relates generally to computer code, and more specifically to a system and method for improved conversion of computer code to target computer byte code of a second type.
2. Description of the Related Art
Traditionally, most computer programs comprised machine-dependent, system-level instructions. A program would be written in a higher level language (source code), such as C or C++, and converted into machine instructions (object code) that could be executed by a computer processor. While the resulting object code could be executed very efficiently, source code compiled on one computer architecture (for example, the Microsoft WINDOWS® operating system environment on an Intel PENTIUM® processor-based computer system) could not subsequently run on a different architecture (such as an Apple MACINTOSH® operating system environment on a POWERPC™ processor-based computer system) (WINDOWS is a registered trademark of Microsoft Corp., PENTIUM is a registered trademark of Intel Corp., MACINTOSH is a registered trademark of Apple Computer, Inc., and POWERPC is a trademark of International Business Machines Corp.). To properly execute a program on different computer architectures, programmers typically undertook steps to re-compile source code for each target architecture. Additionally, machine-specific differences often required significant revision to the program's source code in order to even enable recompilation for a different architecture.
A modern innovation to this traditional method of compiling source code into machine-level object code is to use intermediate byte languages and byte code interpreters. Byte code (also known as “bytecode” or “byte-code”) is a form of intermediate language that is typically more abstract than object code, but closer to machine language than a higher level language. Examples of languages that compile to byte code include JAVA™ from Sun Microsystems, Inc. and languages that target the Common Language Infrastructure (CLI) from Microsoft Corporation (JAVA is a trademark of Sun Microsystems, Inc.). A program that utilizes byte code is initially programmed in source code. The source code is then compiled into byte code. Compiled Java byte codes, for example, are typically in the form of “.class” or “.jar” files. The Common Language Infrastructure is an implementation of the Standard ECMA-335 specification. Source code written under the Common Language Infrastructure can be compiled to Common Intermediate Language (CIL) byte code. Common Intermediate Language byte code is typically packaged in a .Net Assembly, which can comprise Common Intermediate Language byte code, assembly metadata, type metadata and other resources. A .Net Assembly may be a standalone file or comprise multiple files. Metadata known as the assembly manifest describes how the elements in a given assembly relate to each other. Compiled byte code, whether standalone or contained in a larger package, can be interpreted by a byte code interpreter (also called a virtual machine) that translates the byte codes into machine level instructions. Examples of virtual machines include the Java Virtual Machine from Sun Microsystems and the Common Language Runtime (CLR), also called the Virtual Execution System, from Microsoft Corporation.
Thus, by way of example, a programmer using the Common Language Infrastructure can program an application in higher-level language such as Microsoft's C# or Visual Basic .Net and compile the program source code into Common Intermediate Language byte code and package it into a .Net Assembly. The resulting byte code can then be run in the CLR.
Typically, a virtual machine is available for different computer architectures. The virtual machine can take input from a program compiled in a standard byte code form and run the program on the native computer architecture in which the machine resides. Thus, in contrast to machine-specific object code, a byte code program can run in a virtual machine on any different architecture (that has a virtual machine) without a recompilation or reprogramming of the underlying source code. By way of example, a Java program compiled into byte code could run without modification in a virtual machine on both an Apple Macintosh computer and a Microsoft Windows computer.
During this same time, markup languages such as eXtensible Markup Language (XML) have gained popularity for their data description capabilities. Markup languages generally describe data and user interfaces as well as the details of the structure and appearance of both. Although most markup languages typically comprise ASCII text, markup language files may alternatively be serialized in a binary form, such as Microsoft's Binary extensible Application Markup Language (BAML). Markup languages such as HTML are well known for defining text and layout descriptions. Graphics markup languages such as the Scalable Vector Graphic (SVG) XML-based markup language can describe two-dimensional vector graphics. Scripting markup languages allow a programmer to add functional program code to markup language code that may then execute in a web server and dynamically output different markup language code. Exemplary scripting markup languages include Java Server Pages (JSP), Hypertext Preprocessor (PHP), Cold Fusion Markup Language (CFML) and Active Server Pages (ASP). For example, a programmer could create a web page comprised of mostly HTML tags and further including a CFML tag that inserted the current date and time every time the page was accessed. Upon access by a client web browser, the CFML code would execute and the web browser would receive an HTML page with the current date and time inserted as HTML data by the CFML code. Additionally, extensible languages such as XML allow programmers to define their own customized tags. This extensibility allows programmers to define, validate and interpret data exchanged between applications, even as the underlying data formats change over time.
When used in conjunction with functional programming language code, markup languages can be used inter alia to define the layout and appearance of objects in a program. For example, Microsoft's eXtensible Application Markup Language (XAML), an XML-based language, allows a programmer to define user interfaces and instantiate objects defined in Common Intermediate Language and contained in .Net Assembly packages. XAML and Common Intermediate Language code can be cross-referenced and executed by the Common Language Runtime. As an alternate example, XML User Interface Language (XUL) from the Mozilla Foundation is an XML-based language that can similarly describe the window layouts and user interfaces for modular software components written in languages including C, C++, and JavaScript using the Cross Platform Component Object Model (XPCOM) framework.
While byte code software applications, particularly when used in conjunction with markup language code, are quite useful and portable, one disadvantage of these approaches is that byte code of one type cannot be easily executed by a byte code interpreter of another type or converted efficiently to byte code of another type. Thus, although byte code may generally overcome machine-dependency, there is some level of dependency on a specific byte code interpreter application. Developers generally have to manually re-code applications for different byte code interpreters, which can be quite difficult in the case where source code is unavailable and only compiled byte code is on hand. Although some tools exist to disassemble compiled byte code into an assembly language or higher level language, a developer still has to port that source code to a different byte code language type in order to convert byte code of a first type into byte code of another type. In these respects, creation of target byte code according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides a system and method of byte code creation that is more flexible, robust and efficient than conventional byte code creation methods.